Durometer Digital vs Regular

I have a regular Long Acre Durometer. I follow the directions and take the reading as soon as the tire is punched. I still don't feel the reading is as accurate as it should be given the importance of these tires. Seems one reading to the next can be as much as 4 points off. Then the other day I dropped the damn thing on the concrete and it was reading consistently 10 points off. You can turn the dial and adjust it when tested against a known object, but I'm still not convinced I didn't damage this thing.

Are the digital duros the same where the constantly change, or do thy just punch and lock a number?

ABR #69

It's the nature of rubber, Duro is important, but it's not the end all be all when it comes to tires. Some guys will tell you they don't even use one. They're mainly a comparative tool, there is a standard by which it's measured and calibrated as a measuring tool, so you should send it back to Long Acre and have it repaired or replaced. BUT, when it comes to the digital, they're going to fluctuated with readings. But, you're mainly wanting to compare between two sets of tires and get a sort of general feel of where they're at.

If I win with a set of tires and my duro reads 52 on that set of tires, and yours says 50(When it's calibrated) Then it's just a reference, it's not a 100% hard and fast rule it has to be that duro. It's more a ballpark and going by your gut feeling as to what it should be by small nuances of how the tires wear if it could be a tad softer or harder. It all comes with time and practice.

Bottom line is replace it with a digital, or have it repaired or replaced, but it should be calibrated at the least.


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Personally, I'm not fond of the digital durometers.
I find the older dial gauges to be more consistent when taking readings.
The digital will vary while taking readings, which negates the advantage of reading an actual number on the screen. If the numbers are always changing, which one do you choose? Answer is be consistent when you read them - same as a dial gauge in that respect, I guess.
Don't get me wrong, digital is nice, but I wouldn't trade my old dial gauge for one.

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Brian Carlson
Carlson Racing Engines
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Linden, IN


There are tiny gears inside of it and a spiral spring. What happens when you drop it is, the gears skip a tooth or more. I have successfully fixed mine twice now. It is something you really have to be patient doing. But mine reads 0 when it is at rest and 100 when I press it on steel so I believe it to be accurate.
I am consistant with mine so mine could read 5 points higher or lower than someone else's but I only use mine and am consistent with it and what points the track wants so whatever points mine reads is what I will use for that track. That is why I am always consistent with the same one. Just like scaling...always scale in same place with each scale under the tire it is always under and everything identical to how it was last time to keep everything consistent. Regular has my vote but if you are constant with only using 1 digital you should be fine but I have seen them throw weird numbers in the cold and stuff.